Assemblies for connecting a diode to an optical fiber are known. In such conventional assemblies, optical emission from the diode is normally transmitted successively through different transparent materials having different indices of optical refraction.
A difficulty often encountered with such connector assemblies is that the optical emission is scattered at the boundaries between transparent materials of different indices. Another difficulty is that the optical emission can reflect from surfaces of the materials or from a junction of one of the materials with an air gap. In the event the diode is a laser diode, and the emission is reflected backward at low angles of incidence to the reflecting surface, such backward reflections can enter the laser diode and cause instability of the diode.
A connector assembly designed to overcome the aforementioned disadvantages is disclosed by U.S. Pat. No. 4,979,791, which is assigned to the assignee of the present application. The connector assembly of U.S. Pat. No. 4,979,791 eliminates backward reflections and the pigtail coupling commonly employed where bare optical fibers are coupled to a laser package. The connector assembly of U.S. Pat. No. 4,979,791 provides a disconnectable coupling for an optical fiber to a laser diode which includes a connector body encircling an optical focusing element, the laser diode having an emission axis aimed along the axis of the focusing element, and a coupling element contacting the focusing element without an air gap therebetween. The focusing element is adapted to convert diverging optical emission of the laser diode into a converging beam, and the coupling element is intended to receive the converging beam without backward reflection and to transmit the converging beam to the optical fiber.
A common concern of known disconnectable connector assemblies for connecting laser diodes to optical fibers is the potentially hazardous situation presented when the optical fiber is disconnected from the assembly while the laser diode is operative (that is, the diode is emitting radiation at the time of disconnection) inasmuch as an operator inadvertently coming into visual contact with the laser emission may suffer eye injury, possibly even loss of vision. A need, therefore, exists for a connector assembly that reduces the laser emission to a safe and non-injurious level while still effectively and operatively coupling the laser diode to the optical fiber.
In addition, there are many applications where it is desirable to have the capability of reducing or controlling the power of the light entering into the optical fiber.